Innerless catheter

ABSTRACT

An over-the-wire balloon catheter for use in angioplasty includes a proximal single lumen shaft and a multilumen distal portion on which an inflatable balloon is mounted. The lumen of the shaft acts as a combined inflation lumen and guide wire lumen. In the multilumen distal portion, a distal inflation lumen connects the combined lumen with the interior of the balloon, while the distal guide wire lumen extends through the balloon to provide a passage for a guide wire.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of angioplasty. Inparticular, the present invention relates to a dilatation ballooncatheter.

2. Description of the Prior Art

Angioplasty has gained wide acceptance in recent years as an efficientand effective method for treating types of vascular diseases. Inparticular, angioplasty is widely used for opening stenoses in thecoronary arteries, although it is also used for treatment of stenoses inother parts of the vascular system.

The most widely used form of angioplasty makes use of a dilatationcatheter which has an inflatable balloon at its distal end. Usingfluoroscopy, the physician guides the catheter through the vascularsystem until the balloon is positioned across the stenosis. The balloonis then inflated by supplying a fluid under pressure through aninflation lumen to the balloon. The inflation of the balloon causesstretching of the artery and pressing of the lesion into the artery wallto reestablish acceptable blood flow through the artery.

There has been a continuing effort to reduce the profile and improve thetrackability (flexibility) of the dilatation catheter so that thecatheter can not only reach, but also cross a very tight stenosis. Afurther requirement of a successful dilatation catheter is its"pushability". This involves the transmission of longitudinal forcealong the catheter from its proximal end to its distal end so that aphysician can push the catheter through the vascular system and thestenosis.

Two types of dilatation catheters are "over-the-wire" catheters and"non-over-the-wire" catheters. An over-the-wire catheter is one in whicha separate guide wire lumen (sometimes called a "thru lumen") isprovided so that a guide wire can be used to establish the path throughthe stenosis. The dilatation catheter can then be advanced over theguide wire until the balloon is positioned within the stenosis. Oneproblem with the over-the-wire catheter is the requirement of a largerprofile and a generally larger outer diameter along its entire length inorder to allow for a separate guide wire lumen.

A non-over-the-wire catheter acts as its own guide wire, and thus thereis no need for a separate guide wire lumen. One advantage of anon-over-the-wire catheter is its potential for reduced profile since aguide wire lumen is not required. However, one disadvantage is theinability to maintain the position of a guide wire within the vascularsystem when removing the catheter and exchanging it for one of a smaller(or larger) balloon diameter. Thus, to accomplish an exchange with thenon-over-the-wire catheter, the path to the stenosis must bereestablished when replacing the catheter with one having a differentballoon diameter.

SUMMARY OF THE INVENTION

The catheter of the present invention includes a main shaft, a secondarydistal outer tube connected to the main shaft at the distal end of themain shaft, a distal inner tube extending through the distal outer tube,an inflatable balloon, which is attached at its proximal end to thedistal outer tube and at its distal end to the distal inner tube. Themain shaft is an elongate hollow thin-walled metal tube having aproximal end and a distal end, and having a lumen extending therethroughfrom the proximal end to the distal end which functions as both aninflation lumen and a guide wire lumen. A distal inflation lumen isdefined between the distal outer tube and the distal inner tube and isin fluid communication with the combined inflation/guide wire lumen ofthe main shaft and with the interior of the balloon. The distal innertube has a distal guide wire lumen which is aligned with the combinedlumen of the main shaft and extends through the balloon to provide apassageway for a guide wire.

In preferred embodiments an insert provides a fluid path between thecombined lumen and the distal inflation lumen, and provides a platformfor connecting the main shaft to the distal inner and outer tubes.

The resistance to fluid flow between the combined lumen and the interiorof the balloon is substantially less than the resistance to fluid flowbetween an outer surface of the guide wire and an inner surface of thedistal inner tube. This resistance to fluid flow effectively provides anessentially fluid-tight seal between the inner surface of the distalinner tube and the outer surface of the guide wire when positive ornegative fluid pressure is applied to the interior of the balloon.

In one preferred embodiment of the present invention, the insertcomprises a main insert tube having a length substantially shorter thanthat of the distal outer tube and having a plurality of smaller diameteropenings (e.g., small tubes) disposed evenly about the main insert tubefor providing a fluid path between the combined lumen and the distalinflation lumen. The plurality of small tubes are bonded to an outersurface of the main insert tube.

In another preferred embodiment of the present invention, the insertcomprises an insert tube having a proximal end with a larger diameterthan a distal end thereof, and having radial perforations in the wallsof the insert tube for providing a fluid path between the combined lumenof the main shaft and the distal inflation lumen.

In another preferred embodiment of the present invention, the insertcomprises an insert tube of uniform diameter having tubular slots withinthe walls of the insert tube extending throughout the length of theinsert tube for providing a fluid path between the combined lumen andthe distal inflation lumen.

In another preferred embodiment of the present invention, the insert isintegral with, and of similar construction to, the main shaft and has asmaller outer diameter than the main shaft. The insert has radialperforations in its walls for providing a fluid path between thecombined lumen and the distal inflation lumen. The insert has a smallerdiameter at a distal end thereof and has the proximal end of the distalinner tube member bonded to either an inner surface or an outer surfaceat the distal end of the insert.

In another preferred embodiment of the present invention, the means forproviding a fluid path between the combined lumen and the distalinflation lumen comprises perforations located in the walls of a distalend portion of the main shaft. The distal end portion of the main shaftis integral with and of similar construction to the distal inner tube,and the distal end of the main shaft has a smaller diameter than theproximal end.

In another preferred embodiment of the present invention, the insertcomprises a tubular-shaped member having walls comprised of a permeablematerial such that the walls of the tubular-shaped member act as a fluidpath between the combined lumen and the distal inflation lumen.

In another preferred embodiment of the present invention, the insertcomprises a tubular-shaped member having a multiple ribbed outer surfacewhich forms cavities that act as a fluid path between the combined lumenand the distal inflation lumen.

In another preferred embodiment of the present invention, the insertcomprises a member having a single ribbed outer surface which forms apair of grooves acting as a fluid path between the combined lumen andthe distal inflation lumen.

In another preferred embodiment of the present invention, the insertcomprises a tubular-shaped member having a multiple ribbed inner surfacewhich forms cavities between the tubular-shaped member and the distalinner tube which act as a fluid path between the combined lumen and thedistal inflation lumen.

In another preferred embodiment of the present invention, the insertcomprises a tubular-shaped member having a single ribbed inner surfacewhich forms a pair of grooves between the tubular-shaped member and thedistal inner tube which act as a fluid path between combined lumen andthe distal inflation lumen.

Preferably, the insert of the present invention facilitates theintroduction of a distal end of the guide wire from the combined lumeninto a proximal end of the distal inner tube. To this end, the insertmay include a diametrically sloped guide wire transition guiding surfaceto direct the distal end of the guide wire into the proximal end of thedistal inner tube.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a balloon catheter system of the present invention, withsome parts broken away and shown in section.

FIG. 1B is an enlarged sectional view of the distal end of the ballooncatheter of FIG. 1.

FIG. 2 is a detail sectional view of the inflatable balloon bonded tothe distal outer tube of the balloon catheter of the present invention.

FIG. 3 is a detail sectional view of the connection of the main shaft,distal inner and outer tubes and insert of the balloon catheter of thepresent invention.

FIG. 4A is a detail lateral sectional view showing one preferredembodiment of the insert of the balloon catheter of the presentinvention.

FIG. 4B is a sectional view along lines 4B--4B in FIG. 4A.

FIG. 5A is a detail lateral sectional view of an insert used in anotherpreferred embodiment of the balloon catheter of the present invention.

FIG. 5B is a sectional view along lines 5B--5B in FIG. 5A.

FIG. 6A is a detail lateral sectional view of an insert which is anotherpreferred embodiment of the balloon catheter of the present invention.

FIG. 6B is a sectional view along lines 6B--6B in FIG. 6A.

FIG. 7 is a detail sectional view of an insert which is anotherpreferred embodiment of the balloon catheter of the present invention.

FIG. 8 is a detail sectional view of another preferred embodiment of theballoon catheter of the present invention.

FIG. 9 is a detail sectional view of another preferred embodiment of theballoon catheter of the present invention.

FIG. 10 is a detail lateral sectional view of an insert which is anotherpreferred embodiment of the balloon catheter of the present invention.

FIG. 11 is a detail lateral sectional view of an insert which is anotherpreferred embodiment of the balloon catheter of the present invention.

FIG. 12 is a detail lateral sectional view of an insert which is anotherpreferred embodiment of the balloon catheter of the present invention.

FIG. 13 is a detail lateral sectional view of an insert which is anotherpreferred embodiment of the balloon catheter of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Dilatation balloon catheter 10 shown in FIGS. 1A and 1B includes mainshaft 12, distal outer tube 14, insert or plug 16, distal inner tube 18,and balloon member 20. Connected at the proximal end of main shaft 12 ismanifold 21, which is adapted to be connected to an inflation device(not shown) for inflating and deflating balloon 20. Guide wire 22extends through manifold 21, main shaft 12, and distal inner tube 18,and out the distal end of catheter 10.

Main shaft 12 is an elongated flexible thin-walled tube, preferably ofstainless steel or polyimide with a low friction coating such asPARYLENE (Poly p-xylylene), TEFLON (PTFE Fluorocarbon), or siliconerubber. In the embodiment shown in FIGS. 1A and 1B, main shaft 12 has aninside diameter of about 0.029 inch, and outside diameter of about 0.031inch, and a shaft coating thickness of about 0.001 inch. Main shaft 12is mounted at its proximal end to manifold 21 which is connected to aninflation device (not shown) to provide positive fluid pressure to lumen24 of main shaft 12 for balloon inflation, and negative fluid pressurefor balloon deflation. Of course, the manifold has a diaphragm orTouhy-Borst type fitting relative to the guide wire and proximal end ofthe manifold to permit selective closure of a hermetic seal about theguide wire when the combined lumen is inflated or deflated. Opening ofthe fitting permits guide wire movement, while closure thereof preventsfluid from escaping out of the manifold adjacent the proximal endthereof and the guide wire.

Mounted at the distal end of main shaft 12 is distal outer tube 14,which extends from the distal end of main shaft 12 to the proximal endof balloon member 20. Distal outer shaft 14 is a hollow, flexible, andpreferably torque transmitting shaft which has greater flexibility thanmain shaft 12. Distal inflation lumen 26 (which is defined by theannular space between distal outer tube 14 and distal inner tube 18) isin fluid communication with lumen 24 of main shaft 12 and connects lumen24 with the interior of balloon member 20.

Balloon member 20, which is preferably a polymer material such as apolyolefin or polyimide, includes proximal bond segment 28, distensibleballoon segment 30, and small diameter distal segment 32. FIG. 2 showsproximal bond segment 28 bonded to the distal end of distal outer tube14. FIG. 2 is a magnified view of a portion of FIG. 1B, showing infurther detail distal outer shaft 14, distal inner shaft 18, guide wire22, distal inflation lumen 26, proximal bond segment 28 of balloonmember 20, and distensible balloon segment 30 of balloon member 20.

FIG. 3 shows in detail insert 16, which is preferably a metallic orpolyimide tubing and which provides a platform for connecting main shaft12 and distal outer and inner tubes 14 and 18. Insert 16 also provides afluid path between lumen 24 and distal inflation lumen 26. FIG. 3 is amagnified view of a section of FIG. 1B showing in further detail mainshaft 12, distal outer tube 14, insert 16, distal inner tube 18, guidewire 22, lumen 24 of main shaft 12, distal inflation lumen 26, mainshaft/distal outer tube/insert bond 34, fluid path 36 of insert 16, anddistal guide wire lumen 38.

FIG. 3 shows in greater detail how main shaft 12 and distal outer tube14 are connected, and how insert 16 provides a platform and a fluid pathbetween main shaft lumen 24 and distal inflation lumen 26. The distalend of main shaft 12 is bonded to the proximal end of distal outer tube14 at bond 34. Insert 16 acts as a platform for bond 34 to support theconnection between main shaft 12 and distal outer tube 14. The innersurface of main shaft 12 and the inner surface of distal outer tube 14are bonded to the outer surface of insert 16 at bond 34. Insert 16includes fluid path 36 which provides a flow path for fluid between mainshaft lumen 24 and distal inflation lumen 26. An inner surface of insert16 is bonded to the outer surface of distal inner tube 18. A proximalend of distal inner tube 18 is located at insert 16 and extends throughdistal outer shaft 14 and balloon member 20. A distal end of distalinner shaft 18 is connected to the distal end of balloon member 20, asseen in FIG. 1B.

As is shown in greater detail in FIG. 3, guide wire 22 extends throughlumen 24 of main shaft 12 and distal guide wire lumen 38 of distal innertube 18, and out the distal end of catheter 10. The inner diameter ofdistal inner tube 18 and the outer diameter of guide wire 22 are closelymatched so that guide wire 22 occupies most of the cross-sectional areaof guide wire lumen 38, leaving only a small fluid path within lumen 38.The fluid resistance of guide wire lumen 38, when guide wire 22 isextending through it, is far greater (e.g., about 50 times greater) thanthe fluid resistance from lumen 24 through insert 16 and distalinflation lumen 26 to the interior of balloon 20. This configurationallows for inflation/deflation without perceptible fluid flowing out thedistal end of distal guide wire lumen 38 during inflation(pressurization through manifold 21), and without perceptible passage offluid (blood) into lumen 38 and/or lumen 24 during deflation (vacuumapplied through manifold 21.)

With the dilatation catheter 10 of the present invention, there is ineffect a proximal single lumen portion (main shaft 12) and a distalmultiple lumen portion (formed by distal outer tube 14 and distal innertube 18). Lumen 24 of main shaft 12 functions as a combined inflationand guide wire lumen to which both distal inflation lumen 26 and distalguide wire lumen 38 are connected. The present invention allows thecatheter 10 to have a smaller outer diameter because of using only asingle lumen proximally while retaining the advantages of anover-the-wire catheter due to the multilumen distal portion. This isaccomplished by providing a fluid flow path between the combined lumen24 and the interior of balloon 20 which has a much lower fluidresistance than there is through the distal guide wire lumen 38 whenguide wire 22 is in place. The fluid flow resistance differential is aresult of difference in cross-sectional area of the inflation lumen andthe guide wire lumen for fluid flow, and from the fact that the muchsmaller guide wire lumen cross-sectional area extends longitudinallymuch further than the larger inflation lumen.

In the embodiment shown in FIGS. 1A, 1B, 2 and 3, distal outer tube 14is preferably made of a flexible polymeric material such as high densitypolyethylene (HDPE), and has an inner diameter of about 0.026 inch, andan outer diameter of about 0.032 inch. Distal inner tube 18 ispreferably a flexible polymeric material such as polyimide and has aninner diameter of about 0.012 inch, and an outer diameter of about 0.014inch with a lubricious inner surface, such as apolyimide-polytetrafluoroethylene composite material.

In the following discussion and in FIGS. 4A-14, various embodiments ofthe present invention are shown which illustrate different ways in whicha connection between a single lumen proximal portion and a multilumendistal portion can be made in accordance with the present invention.

FIG. 4A is a front view showing wall insert 40 which includes maintubular member 42, a plurality of circumferentially spaced smalldiameter tubes 44, and bond 46. FIG. 4B is a sectional plan view ofinsert 40 shown in FIG. 4A. In this preferred embodiment of the presentinvention, the plurality of smaller diameter tubes 44 are bonded by bond46 to an outer surface of main tubular member 42. Inner surface 47 ofmain tubular member 42 is bonded to distal inner shaft 18 shown in FIGS.1, 2 and 3. Smaller diameter tubes 44 have channels 48 throughout theirlength which form a fluid path for the inflation medium (from lumen 24of main shaft 12 to inflation lumen 26). Main tube 12 and distal outershaft 14 shown in FIGS. 1, 2 and 3, are bonded by bond 49 to smalldiameter tubes 44 at a point located furthest from the axis of wallinsert 40 on an outer surface of small diameter tubes 44. In thispreferred embodiment, wall insert 40 is composed of metallic orpolymeric tubes 44 that have a length of about 0.25 inch, and are bondedto a main tubular member 42 that has an inner diameter of about 0.015inch, and an outer diameter of about 0.0165 inch.

FIGS. 5A and 5B show insert 50, which is another preferred embodiment ofthe balloon catheter of the present invention. FIG. 5A is a front viewof insert 50, showing proximal insert end 52, distal insert end 54, andtransition region 56. Distal inner tube 18 is bonded to inner bondsurface 57 of distal insert end 54, while main shaft 12 and distal outertube 14 are bonded to outer bond surface 58 of proximal insert end 52(which has a larger diameter than distal insert end 54). In thispreferred embodiment, proximal insert end 52 has an inner surfacediameter of about 0.025 inch, and an outer surface diameter of about0.028 inch. Distal insert end 54 has an inside surface diameter of about0.015 inch, and an outer surface diameter of about 0.018 inch. Insert 50is preferably made of a metallic or polymeric material, and has aplurality of radial perforations 59 in transition region 56 which form afluid path for inflation fluid (as illustrated by arrows 59b in FIG. 5B)between lumen 24 of main shaft 12 and inflation lumen 26. Radialperforations 59 need not be circular, and are located in the walls oftransition region 56, where a diametrical transition occurs betweenproximal insert end 52 and distal insert end 54.

FIGS. 6A and 6B show ring-shaped insert 60, which is another preferredembodiment of the present invention. FIG. 6A is a front view of insert60, which in this embodiment includes a plurality of circumferentiallyspaced, axially extending holes 62 which define fluid paths throughinsert 60. Insert 60 is bonded to distal inner shaft 18 at inner surface66, and is bonded to main shaft 12 and distal outer tube 14 at outersurface 68.

FIG. 7 shows an embodiment in which insert region 70 is an integralportion of main shaft 12 at the distal thereof. Insert 70 includes afirst proximal region 72 of reduced diameter, a second transition region74 and a third distal end region 76. Distal outer tube 14 is bonded toan outer surface 73 of first region 72, while distal inner tube 18 isbonded to an inner surface 75 of third region 76. A plurality of holes78 in second transition region 74 provide a fluid path through insertregion 70 at the distal end of the main shaft 12.

FIG. 8 shows integral insert region 80 similar to insert 70 shown inFIG. 7, except that main shaft 12, distal inner tube 18, and insertregion 80 are an integral unit. A plurality of holes 82 in insert region80 provide the fluid path through insert region 80. In this embodiment,outer tube 14 is bonded to insert region 80 at bond 84, adjacent thetransition portion of insert region 80 between main shaft 12 and distalinner tube 18.

In the embodiments of the present invention shown in FIGS. 5, 7 and 8,the insert has a region of generally progressive diametrical reductionbetween its proximal and distal regions (e.g., transition region 56 inFIGS. 5A and 5B and transition region 74 in FIG. 7) which aids indefining the guide wire lumen for the balloon catheter. Thus, whenlongitudinally inserting a guide wire into the balloon catheter of thepresent invention, a distal end of the guide wire 22 will be gently ledor guided radially inwardly when it contacts the sloped walls of thistransition region toward the opening for the distal guide wire lumen 38at a proximal end of the distal inner tube 18.

FIG. 9 shows insert 90 formed by a ring of porous or permeable material.Main shaft 12 and distal outer tube 14 are bonded to outer surface 92 ofinsert 90, while distal inner tube 18 is bonded to inner surface 94thereof. The fluid path between lumen 24 of main shaft 12 and inflationlumen 26 is through the porous material of insert 90.

FIGS. 10-13 show various ribbed or fluted insert shapes. Insert 100shown in FIG. 10 is a multi-ribbed insert, an annular inner surfacewhich mates with an outer surface of distal inner tube 18, and aplurality of exterior ribs 102 which define fluid paths 104 betweeninsert 100 and shaft 12 (and distal outer tube 14). Insert 110 in FIG.11 has a single exterior rib 112 which defines a pair of fluid paths 114between insert 110 and shaft 12 (and distal outer tube 14). Insert 120of FIG. 12 has an annular outer surface which mates with an innersurface of shaft 12 (and distal outer tube 14), and a plurality ofinwardly projecting ribs 122 which define a plurality of fluid paths 124between insert 120 and distal inner tube 18. Insert 130 in FIG. 13 has asingle rib 132 projecting inwardly from an outer ring portion 134.Distal inner tube 18 is bonded between rib 132 and an inner wall of ring134, and thus, a pair of fluid paths 136 are defined on opposite sidesof rib 132 between the distal inner tube 18 and inner wall of ring 134.

The present invention offers the advantages of a single lumen catheter(primarily, reduced cross-sectional diameter) and a multiple lumencatheter (separate lumens for guide wire and inflation, thereby allowingcatheter exchanges with the guide wire in place) in the same dilatationcatheter. This is achieved by a single lumen proximal portion to whichis attached a multilumen distal portion. Reduced shaft diameter for themain shaft of the dilatation catheter is achieved, while also obtainingthe benefits of an over-the-wire arrangement due to the multilumendistal portion.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

What is claimed is:
 1. A balloon catheter for use with a guide wire, theballoon catheter comprising:a proximal single lumen shaft having a firstlumen extending therethrough from a proximal end to a distal end; adistal outer tube having a proximal end connected to the distal end ofthe shaft and having a second lumen therethrough which is in fluidcommunication with the first lumen; a distal inner tube extendingdistally from the shaft and through the distal outer tube, the distalinner tube having a third lumen therethrough aligned generally with thefirst lumen so that a guide wire can extend through the first lumen andthe third lumen; and an inflatable balloon having a proximal endconnected to a distal end of the distal outer tube, a distal endconnected to a distal end of the distal inner tube, and having aninterior in fluid communication with the second lumen, whereinresistance to fluid flow between the first lumen and the third lumenwhen the guide wire is located in the third lumen is substantiallygreater than resistance to fluid flow between the first lumen and thesecond lumen.
 2. The balloon catheter of claim 1 and furthercomprising:insert means attached to the shaft and extending into distalouter tube for providing a connection between the proximal end of thedistal inner tube and the distal end of the shaft.
 3. The ballooncatheter of claim 2 wherein the insert means includes a fluid passageconnecting the first lumen and the second lumen.
 4. The balloon catheterof claim 3 wherein the distal end of the shaft is bonded to the proximalend of the distal outer tube and to an outer surface of the insertmeans.
 5. The balloon catheter of claim 3 wherein the insert means has alength substantially shorter than that of the distal outer tube.
 6. Theballoon catheter of claim 5 wherein an inner surface of the insert meansis bonded to an outer surface of the distal inner tube.
 7. The ballooncatheter of claim 6 wherein an outer surface of the insert means isbonded to an inner surface of the shaft and an inner surface of thedistal outer tube.
 8. The balloon catheter of claim 7 wherein the insertmeans comprises a main tubular member having a plurality of smalldiameter openings therethrough surrounding the main tubular member forproviding a fluid path between the first lumen and the second lumen. 9.The balloon catheter of claim 8 wherein the small diameter openings aredefined by smaller tubes bonded to an outer surface of the main tubularmember.
 10. The balloon catheter of claim 7 wherein the insert meanscomprises a tubular member having a proximal end with a larger diameterthan a distal end and having perforations in the tubular member forproviding a fluid path between the first lumen and the second lumen. 11.The balloon catheter of claim 7 wherein the insert means comprises atubular member having tubular slots extending longitudinally through thetubular member for providing a fluid path between the first lumen andthe second lumen.
 12. The balloon catheter of claim 7 wherein the insertmeans comprises a tubular member made of a fluid permeable material suchthat the tubular member acts as a fluid path between the first lumen andthe second lumen.
 13. The balloon catheter of claim 7 wherein the insertmeans comprises a tubular shaped member having a ribbed outer surface.14. The balloon catheter of claim 7 wherein the insert means comprises agenerally tubular shaped member with a single ribbed outer surface. 15.The balloon catheter of claim 7 wherein the insert means comprises atubular shaped member having a ribbed inner surface.
 16. The ballooncatheter of claim 7 wherein the insert means comprises a tubular shapedmember having a single ribbed inner surface.
 17. The balloon catheter ofclaim 2 wherein the insert means is integral with the shaft, has asmaller diameter than the shaft and has at least one openingtherethrough for providing a fluid path between the first lumen and thesecond lumen.
 18. The balloon catheter of claim 17 wherein the insertmeans has a smaller diameter at a distal end thereof, with the distalend of the insert means being bonded to the proximal end of the distalinner tube.
 19. The balloon catheter of claim 1 wherein the distal endof the shaft has a reduced diameter portion and has an opening thereinfor providing a fluid path between the first lumen and the second lumen,the distal end of the shaft being integral with the distal inner tube.20. The balloon catheter of claim 1 wherein the shaft is a thin wallmetal tube.
 21. The balloon catheter of claim 1 and furthercomprising:insert means positioned between the first lumen and the thirdlumen for facilitating the introduction of a distal end of the guidewire longitudinally into the third lumen from the first lumen.
 22. Aballoon catheter for use with a guide wire, the balloon cathetercomprising:a proximal single lumen shaft having a first lumen extendingtherethrough from a proximal end to a distal end, the first lumenproviding a passage for the guide wire and inflation fluid in theballoon catheter; a multilumen distal portion connected to the distalend of the single lumen shaft at a transition zone and having a secondlumen and a third lumen extending distally therefrom, the second lumenbeing in fluid communication with the first lumen for transmission ofthe inflation fluid, and the third lumen being aligned with the firstlumen to permit longitudinal movement of the guide wire therein; and aninflatable balloon attached to the distal portion and spaced distallyfrom the transition zone, with an interior of the balloon being in fluidcommunication with the second lumen and with the third lumen extendingthrough the balloon.
 23. The balloon catheter of claim 22 wherein themultilumen distal portion provides greater flexibility than the singlelumen shaft.
 24. The balloon catheter of claim 22 wherein the shaft is athin wall metal tube or polyimide tube.
 25. The balloon catheter ofclaim 22 and further comprising:insert means in the transition zone forconnecting the single lumen shaft and the multilumen distal portion, andfor providing a fluid path between the first and second lumens.
 26. Theballoon catheter of claim 25 wherein the distal end of the shaft isbonded to an outer surface of the insert means.
 27. The balloon catheterof claim 25 wherein the insert means has a length substantially shorterthan that of the multilumen distal portion.
 28. The balloon catheter ofclaim 27 wherein the insert means comprises a main tube having aplurality of small diameter openings disposed circumferentially aboutthe main tube for defining the fluid path between the first and secondlumens.
 29. The balloon catheter of claim 28 wherein the plurality ofsmall diameter openings are defined by smaller tubes bonded to an outersurface of the main tube.
 30. The balloon catheter of claim 25 whereinthe insert means has a proximal portion with a larger diameter than adistal portion and having openings in a transition portion between theproximal and distal portions for defining the fluid path between thefirst and second lumens.
 31. The balloon catheter of claim 25 whereinthe insert means comprises a tube of generally uniform diameter whichhas a plurality of longitudinally extending tubular slots within thetube for defining the fluid path between the first and second lumens.32. The balloon catheter of claim 25 wherein the insert means isintegral with the shaft, has a smaller outer diameter than the shaft,and has openings therein for defining the fluid path between the firstand second lumens.
 33. The balloon catheter of claim 25 wherein theinsert means comprises a tubular shaped member of a fluid permeablematerial such that the tubular shaped member itself acts as the fluidpath between the first and second lumens.
 34. The balloon catheter ofclaim 25 wherein the insert means comprises a tubular shaped memberhaving a multiple ribbed outer surface for forming cavities therebetweento define the fluid path between the first and second lumens.
 35. Theballoon catheter of claim 25 wherein the insert means comprises agenerally tubular shaped member having a single ribbed outer surface forforming a pair of grooves to define the fluid path between the first andsecond lumens.
 36. The balloon catheter of claim 25 wherein the insertmeans comprises a tubular shaped member having a multiple ribbed innersurface for forming cavities between the tubular shaped member and themultilumen distal portion to define the fluid path between the first andsecond lumens.
 37. The balloon catheter of claim 25 wherein the insertmeans comprises a tubular shaped member having a single ribbed innersurface for forming a pair of grooves between the tubular shaped memberand the multilumen distal portion to define the fluid path between thefirst and second lumens.
 38. The balloon catheter of claim 22, andfurther comprising:insert means positioned in the transition zonebetween the first lumen and the third lumen for facilitating theintroduction of a distal end of the guide wire longitudinally into thethird lumen from the first lumen.